Dairy relates to milk — dairy products, a dairy farm. A diary is a book in which you record daily events or appointments. The letters are transposed, both are common words, and spellcheck cannot help, which is why the swap reaches print regularly.
The core difference
Two everyday words separated by a letter swap.
- dairy — of milk: dairy-free, the dairy aisle.
- diary — a daily record: keep a diary.
A way to remember it
Diary contains di-, as in diurnal and daily — both from Latin dies, day. Dairy comes from Middle English deye, a female servant who made butter and cheese. So the day-word has the day-letters.
The British sense of diary
In British English a diary is also an appointments book — "put it in my diary" means schedule it. American English would say calendar or planner, reserving diary for a personal journal.
Frequently asked questions
Which spelling is the journal?
Diary. Dairy relates to milk.
How do I remember which is which?
Diary shares its di- with diurnal and daily, from Latin dies, day.
Does diary mean the same in British and American English?
Not quite. In British English it also means an appointments book; American English uses calendar or planner for that.